1. Field of the Invention
The present disclosure relates to a composition comprising N-acetyl-L-cysteine or its derivatives for treating anxiety disorder. Particularly the present composition is useful in treating anxiety disorders such as post-traumatic stress disorder and phobia.
2. Description of the Related Art
According to the Epidemiological Survey of Mental Disorders in Korea recently performed on 6,114 people between ages 18 to 64 by Seoul National University and National Mental Hospital, the lifetime prevalence of mental disorder was found to be about 34%. This indicates that one out of every three adults suffers from the illness at least once during their lifetime. Particularly, the survey shows that the lifetime prevalence of anxiety disorder including obsessive-compulsive disorder, post-traumatic stress disorder (PTSD), phobia and the like counts for 6.4% of the total illness.
It has been shown that through a widely used fear conditioning method in animal model, the limbic system such as amygdaloid body and nucleus accumbens are involved in the development of PTSD. Recently it has also been suggested that prefrontal lobe was involved in the return of fear memories (Moussawi et al., 2009, Nat. Neurosci. 12(2):182-9). In addition, it has been shown that the changes in the expression of receptors and the secretion of glutamate in the amygdaloid body and prefrontal lobe play an important role in the maintenance of fear memories. The treatment of PTSD and phobia has been hampered by the return fear memories. The available treatments for PTSD and phobia include cognitive restructuring, group therapy, exposure therapy, selective serotonin reuptake inhibitors (SSRI) and the like. However, they are symptomatic therapy and only temporary. Therefore there are demands for the new therapy.
Among them exposure therapy is a behavior therapy, which involves reliving a traumatic situation or confrontation with a feared object, situation, thought or memory in a controlled and therapeutic environment. It is considered to be one of the most effective treatments for the condition due to its effectiveness in reducing the symptoms of PTSD. However, it has some clinical limitations. Exposure therapy is not permanent and the symptoms return in an unexpected time, place and/or situation. Many researches have been done to prevent the return of fear memories after exposure therapy (Schiller et al., 2010, Nature 463: 49-53; Kindt et al., 2009, Nat. Neurosci. 12(3): 256-8). Further the combined use of a drug together with exposure therapy has been done to improve the efficacy of the therapy and to overcome the limitations (Ressler et al., 2004, Arch. Gen. Psychiatry 61: 1136-44).
Currently there are only limited drugs available to treat anxiety disorder such as PTSD and phobia, the efficacy of which is only marginal and temporary.